| 摘要 |
A method including: a first writing step for writing data by injecting electrons into the floating gate; a first verifying step for verifying whether the threshold voltage is higher than the first reference level after performing the first writing operation; a step of repeating the first writing step and the first verifying step until the threshold voltage becomes higher than the first reference level, if the threshold voltage is lower than the first reference level; a second verifying step for verifying whether the threshold voltage is higher than a second reference level which is set to be higher than the first reference level, if the threshold voltage is higher than the first reference level; a step of ending the writing operation if the threshold voltage is lower than the second reference level; and a second writing step for writing data by discharging electrons from the floating gate until the threshold voltage becomes higher than the first reference level and lower than the second reference level, if the threshold voltage is higher than the second reference level.
|
